In Queens, N.Y., at Public School 177, Mayor Michael Bloomberg said that 82 of 380 students have called in sick. Two public schools in New York, both in Queens, have been closed due to the swine flu.Health officials are also considering closing a parochial school inManhattan.

New York and Mexico City — President Obama, at the behest of public-health officials, is recommending that schools with confirmed or suspected cases of swine flu "strongly consider temporarily closing so we can be as safe as possible."

Mexican officials have already taken that step and closed all schools nationwide until at least May 6.

The goal is to keep the flu from spreading. But the request brings up a glaring disconnect between the needs of public health and the majority of workplace policies, at least in the United States.

Nearly half of the people who work for private employers in the US have no paid sick leave, according to an analysis of data from the Bureau of Labor Statistics. Among low-income workers in private employment, almost 80 percent have no paid sick time.

Of those workers in private employment who have paid sick leave, only a third can take a paid sick day to care for an ill child.

So when a school closes, it can create chaos.

"School being shut is the worst thing that can happen for parents who work," said Tina Schiller, who on Tuesday was picking up her young daughter, as usual, from Public School 234 in lower Manhattan. "Remember that one snow day? That was enough to put people over the edge."

There are now hundreds of suspected cases of swine flu in 10 US states. Two public schools in New York, both in Queens, have been closed. Health officials are also considering closing a parochial school in Manhattan. Several schools in California, Illinois, and Texas have closed as well after students tested positive for swine flu. And more are expected to shut their doors in coming days if the flu spreads.

"It's a very serious thing to close down a school or a school system because parents need to work. It's almost easier to shut down a whole city rather than one part of it," says Nicholas Freudenberg, professor of urban public health at Hunter College in New York City. "If you shut down schools and you don't shut down workplaces, what are the parents with a 7-year-old going to do?"

The Family and Medical Leave Act, which was passed in 1993, does require large employers to give workers 12 weeks of unpaid leave in the case of serious illness or that of a child. But to become eligible, a person must work for a company that has more than 50 employees, and they must have worked there at least 12 months and for more than 1,250 hours (about 30 weeks of 40 hours each) in the preceding 12 months. As a result, many low-wage workers don't qualify for the unpaid leave.

Currently, only three cities in the US require companies to offer paid sick leave: San Francisco, Milwaukee, and Washington. Bills to require paid sick leave are pending in several states as well as in Congress. The proposed Healthy Families Act would require employers to guarantee workers seven days of paid sick leave a year to "recover from a short term illness, to care for a sick family member, to seek medical care or to seek assistance related to domestic violence," according to a letter sent to Democratic members of Congress from the bill's sponsors, Sen. Edward Kennedy (D) of Massachusetts and Rep. Rosa DeLauro (D) of Connecticut.

Opponents of the bill say it would impose too many costs and restrictions on small businesses. Advocates say it would remedy the current disconnect between public-health needs and many current workplace policies.

"Even before the swine flu outbreak, there's been a growing recognition that public-health and workplace polices are indeed connected," says Kevin Miller, a researcher at the Institute for Women's Policy Research in Washington. "If a person can't stay home, there are real consequences, particularly for people who work with the public like food-service workers, who are the least likely to have paid sick leave."

Working parents in Mexico are already coping with the problem of how to take care of their children. On Monday, Mexican officials took the unprecedented step of closing all schools nationwide. On Tuesday, Teresa Castillo was in a park throwing a ball back and forth with her two children, including a first-grader.

She considers herself fortunate. "I don't work, so I can be with them," she says. But her cousins have had to scramble to find family members to care for their children. "If this goes on, I will pitch in, too," she says.

The Castillos were practically alone in the park. Most parents, such as Julia Gomez, have opted to keep their children indoors.

Ms. Gomez is a domestic worker who has had to place child care in the hands of her cousin, with whom she lives. It's a challenge, she says, to keep her active, 10-year-old son indoors all day, but she's not willing to take any risks.

The strong family networks in Mexican society, she adds, have lessened the consequences of schools closing down.

"In the US, this would be a catastrophe," Gomez says, since many working parents would have nowhere to place their children. But in Mexico, she says, "there is more often than not a grandparent, or cousin, or sibling nearby."

Outside PS 234 on Tuesday, many parents picking up their children voiced dread at the prospect of schools closing, but also a determination to keep their children safe. (PS 234 is not one of the schools that has closed.)

"It would be a big problem," said Tina Lichtman, holding her young son's hand as she waited to cross the street. "I work freelance so I could manage, and I think we would have to manage if it was a time of crisis. But I also think we have to be careful not to blow things out of proportion."

Across the street, parents and students were lining up in front of an ice-cream truck. There, Christine Scuillio, a working mother of two, said that school closures would put her "in a bind." Her children, she said, could come to her studio where she works in video production. But that could only last for so long. "It could get difficult," she said.